Cytokines such as G-CSF, M-CSF, GM-CSF (colony stimulating factors) and IL-1, IL-3, IL-6 (interleukins) can stimulate hematopoiesis in diseases associated with bone marrow failure and thus accelerate recovery from neutropenia as reported by Metcalf, D., Science, 529, (1991) and H. G. Klingemann and H. J. Deeg, CIPS, 14, 243, (1989) as well as G. Mortsyn and A. W. Burgess, Cancer Research 48, 5624, (1988). Portions of the natural bacterial cell wall and synthetic lipopeptides that mimic the cell wall have been reported to have immunostimulant properties as described by J. Freund, Adv. Tubercl. Res., 1, 130 (1956); F. Ellouz, A. Adam, R. Ciorbaru and E. Lederer, Biochem. Biophys. Res. Commun., 59, 1317, (1974); V. St. Georgiev, Medicinal Res. Rev, 11, 81, (1991) and I. Azuma, Int. J. Immunopharmac., 14,487 (1992). More specifically, certain compounds have been identified which appear to induce the formation of CSF and can aid in bone marrow restoration after myelosuppression caused by chemotherapy or radiation. These include compounds such as pimelautide (RP-40639), [as reported by F. Floch'h, J. Bouchaudon, C. Fizames, A. Zerial, G. Dutruc-Rosset and G. H. Werner, CIPS, 763 (1984) and in Patent No. FR-2,482,961, (1981)]; muroctasin (Daiichi Seiyaku Co.) [as reported by I. Azuma, Int. J. Immunopharmac., 14,487 (1992); R. Nakajima, Y. Yshida, K. Akahane, M. Sekiguchi and Y. Osada, Arzneim.-Forsch., 41, 60, (1991); Scrip, 22, 1655 (1991); and Patent No. EP-135,788, (1985)]; and FK-156 and FK-565 (Fujisawa) [as reported by S. Izumi, K. Nakahara, T. Gotoh, S. Hashimoto, T. Kino, M. Okuhara, H. Aoki, and H. Imanaka, J. Antibiotics, 566, (1983); K. Nakamura, K. Nakahara, H. Aoki, Agric. Biol. Chem., 48, 2579 (1984); H. Keiji, H. Takeno, S. Okada, O. Nakguchi, Y. Kitaura, and M. Hashimoto, Tetrahedron Lett., 23, 693 (1982) and U.S. Pat. Nos., 4,349,466 and 4,666,890].
U.S. Pat. No. 4,666,890 discloses a synthetic tripeptide which has been reported to have activity as an immunomodulator, for use as an antitumor agent rather than as an adjuvant to chemotherapy. The reported cell-wall components and their synthetic analogs are all peptides incorporating a D-glutamic acid (D-Glu) moiety .gamma.-linked to either lysine (Lys) or diaminopi- melic acid (A.sub.2 pm), with additional peptide bonds or fatty acyl groups flanking the two ends.
The novel urethanes and ureas disclosed in this invention are the first examples of non-peptide analogs of bacterial cell wall components and lack the D-Glu moiety common to prior art. Furthermore, while previous art has provided no branching on the peptide backbone, this invention includes branched analogs that retain the desired activity when synthesized in a specific configuration, and a method of synthesis for these chiral branched analogs.